Chances are you wouldn't look at a three-year-old running around with their friends and think, "That kid's definitely going to grow up to have a serious gambling addiction" or "Boy, is she ever headed for a drug problem." And yet a new study has shown that children's behavior at that age can offer real clues about their risk of suffering from addictions later in life.

The study looked at nearly 1,000 people in New Zealand and tracked them from birth to age 32, looking at their psychological, economic, and intellectual life. This is one of just a few longitudinal studies done that offers insight into addiction, and it's shed a lot of light on the origins of it. In short, what the researchers have just found is that kids who were labeled "undercontrolled" when they were three were more than twice as likely to have problems with gambling later (at age 21 and 32) than were their well-adjusted peers. And it's not just gambling. An earlier analysis of data from this study found that undercontrolled three-year-0lds were more than three times as likely to become addicted to drugs as young adults than their peers with the most self-control.

Being "undercontrolled" means the kids showed a lack of self control, which according to Time, included "rapidly shifting emotions, impulsive and willful behavior and relatively high levels of negative feelings." The researchers found that roughly 10 percent of the children had this kind of temperament at three. Even after factors like IQ, gender, and socioeconomic status were accounted for the association with addiction still held. And when the "undercontrolled" children were assessed as adults, they hadn't changed all that much:

[T]hey still rated high on feelings of alienation and continued to express high levels of negative emotion. They also tended to be less conscientious and less socially agreeable than their peers.

Studies like these that are able to track people over the long terms offer a key insight into how addiction begins. It's long been a question whether partaking in drugs or gambling lead to impulsive behavior and negative emotions or whether people get addicted to drugs or gambling because they're depressed or impulsive and therefore more vulnerable. It's a classic chicken vs. egg question, and this study goes a long way toward addressing it.

According to Wendy Slutske, who is a professor of psychological science at the University of Missouri and is the lead author of the study, "[We] have firmly established that undercontrolled temperament comes before any involvement in gambling." What's less certain is why this undercontrolled temperament is associated with addictive behaviors. Do these behaviors offer an escape from negative emotions? Or do people end up doing them simply because they have poor impulse control? Slutske posits some other explanations:

One possibility is that there are genetic factors that are related to both low self-control and gambling or problem gambling. Another possibility is that children who are low in emotional and behavioral control tend to associate with other undercontrolled children who introduce them to gambling activities.

When taken together, these findings on gambling and drug addiction provide strong evidence that some people are simply born more vulnerable to addiction. It's not that they're hedonists; it's that they have too many negative emotions and an inability to control themselves. This study also offers further proof that addiction does not come just from being exposed to something addictive. While many people might be exposed to gambling or drugs, only a small percentage of them develop addictions—and it's clear that their problem is the result of some pre-existing condition, be in an "undercontrolled" temperament, a mental illness, or some other predisposition.

The good news, in case you're looking at your child wondering if he or she is going to grow up to be a casino-dweller or junkie, is that just because there is this association, doesn't mean that all undercontrolled kids grow up to have gambling or drug addictions. Slutske says,

Although it is remarkable that one can predict whether one will develop a gambling problem in adulthood from a 90-minute observational assessment at age 3, it is also important to understand that an undercontrolled 3-year-old is not doomed to become an adult problem gambler. They are just at increased risk. This means that there were many undercontrolled children — in fact, the majority — who did not have any gambling problems as adults.

Relieved? If we want to prevent young people from growing up to be addicts, this research points to the fact that it's important to help them learn the art of self-control—not just to teach them about the dangers of drugs. (Maybe the "just say no" campaign was onto something after all.) They found that a number of the children in the study outgrew their lack of self-control, eventually learning to manage their impulses just as well as their peers who had it figured out from the start. So, if you're a betting (wo)man, you may be tempted to play a round of Spot the Future Addict next time you're on the playground, but don't put all your money on the kids who look like bad seeds, since they might grow up to surprise you.